I think the point is that you can grant them access in 3 seconds, it’s not like you’re giving an onerous task to someone.
While in implementation your notebook analogy may be right, in practice it’s more similar to the police searching your house and asking you to unlock the basement so they can search there too. It’s not exactly a big ask, it’s as simple as unlocking it with the key you have, so from a legal perspective it’s perfectly reasonable.
From a privacy perspective it’s not great, but I’d argue the control should be on when someone is allowed to rummage through your stuff, it shouldn’t matter if your notebook is physical or on your phone. Practicality changes this of course.